What is wave-particle duality? It is a characteristic of photons and other subatomic particles that behave like waves under some conditions and like particles under others.
Wave-particle duality of matter and light is an important part of quantum mechanics, because it best demonstrates the fact that such concepts as "waves" and "particles", which work fine in classical mechanics, are not enough to explanations of the behavior of some quantum objects.
The dual nature of light gained recognition in physics after 1905, when Albert Einstein described the behavior of light using photons, which were described as particles. Then Einstein published the less famous special relativity, which described light as wave behavior.
Particles exhibiting dual behavior
Best of all, the principle of wave-particle dualityobserved in the behavior of photons. These are the lightest and smallest objects exhibiting dual behavior. Among larger objects, such as elementary particles, atoms, and even molecules, elements of wave-particle duality can also be observed, but larger objects behave like extremely short waves, so they are very difficult to observe. Usually, the concepts used in classical mechanics are sufficient to describe the behavior of larger or macroscopic particles.
Evidence of wave-particle duality
People have been thinking about the nature of light and matter for many centuries and even millennia. Until relatively recently, physicists believed that the characteristics of light and matter must be unambiguous: light can be either a stream of particles or a wave, just like matter, either consisting of individual particles that completely obey the laws of Newtonian mechanics, or being a continuous, inseparable medium.
Initially, in modern times, the theory about the behavior of light as a stream of individual particles, that is, the corpuscular theory, was popular. Newton himself adhered to it. However, later physicists such as Huygens, Fresnel and Maxwell concluded that light is a wave. They explained the behavior of light by the oscillation of the electromagnetic field, and the interaction of light and matter in this case fell under the explanation of the classical field theory.
However, at the beginning of the twentieth century, physicists were faced with the fact that neither the first nor the second explanation couldcompletely cover the area of light behavior under various conditions and interactions.
Since then, numerous experiments have proven the duality of the behavior of some particles. However, the appearance and acceptance of wave-particle duality of the properties of quantum objects were especially influenced by the first, earliest experiments, which put an end to the debate about the nature of the behavior of light.
Photoelectric effect: light is made up of particles
The photoelectric effect, also called the photoelectric effect, is the process of interaction of light (or any other electromagnetic radiation) with matter, as a result of which the energy of light particles is transferred to matter particles. During the study of the photoelectric effect, the behavior of photoelectrons could not be explained by classical electromagnetic theory.
Heinrich Hertz noted back in 1887 that shining ultraviolet light on electrodes increased their ability to create electrical sparks. Einstein in 1905 explained the photoelectric effect by the fact that light is absorbed and emitted by certain quantum portions, which he initially called light quanta, and then dubbed them photons.
An experiment by Robert Milliken in 1921 confirmed Einstein's judgment and led to the fact that the latter received the Nobel Prize for the discovery of the photoelectric effect, and Millikan himself received the Nobel Prize in 1923 for his work on elementary particles and the study of the photoelectric effect.
Davisson-Jermer experiment: light is a wave
Davisson's experience - Germer confirmedde Broglie's hypothesis about the wave-particle duality of light and served as the basis for formulating the laws of quantum mechanics.
Both physicists studied the reflection of electrons from a nickel single crystal. The installation, located in a vacuum, consisted of a nickel single crystal ground at a certain angle. A beam of monochromatic electrons was directed directly perpendicular to the cut plane.
Experiments have shown that as a result of reflection, electrons are scattered very selectively, that is, in all reflected beams, regardless of speeds and angles, maxima and minima of intensity are observed. Thus, Davisson and Germer experimentally confirmed the presence of wave properties in particles.
In 1948, the Soviet physicist V. A. Fabrikant experimentally confirmed that wave functions are inherent not only in the flow of electrons, but also in each electron separately.
Jung's experiment with two slits
Thomas Young's practical experiment with two slits is a demonstration that both light and matter can exhibit the characteristics of both waves and particles.
Jung's experiment practically demonstrates the nature of wave-particle duality, despite the fact that it was first carried out at the beginning of the 19th century, even before the advent of the theory of dualism.
The essence of the experiment is as follows: a light source (for example, a laser beam) is directed to a plate where two parallel slots are made. Light passing through the slits is reflected on the screen behind the plate.
The wave nature of light causes light waves passing through slits tomix, producing light and dark streaks on the screen, which wouldn't happen if light behaved purely like particles. However, the screen absorbs and reflects light, and the photoelectric effect is proof of the corpuscular nature of light.
What is wave-particle duality of matter?
The question of whether matter can behave in the same duality as light, de Broglie took up. He owns a bold hypothesis that, under certain conditions and depending on the experiment, not only photons, but also electrons can demonstrate wave-particle duality. Broglie developed his idea of probability waves not only of photons of light, but also of macroparticles in 1924.
When the hypothesis was proven using the Davisson-Germer experiment and repeating Young's double-slit experiment (with electrons instead of photons), de Broglie received the Nobel Prize (1929).
It turns out matter can also behave like a classical wave under the right circumstances. Of course, large objects create waves so short that it is meaningless to observe them, but smaller objects, such as atoms or even molecules, exhibit a noticeable wavelength, which is very important for quantum mechanics, which is practically built on wave functions.
The meaning of wave-particle duality
The main meaning of the concept of wave-particle duality is that the behavior of electromagnetic radiation and matter can be described using a differential equation,which represents the wave function. Usually this is the Schrödinger equation. The ability to describe reality using wave functions is at the heart of quantum mechanics.
The most common answer to the question of what wave-particle duality is is that the wave function represents the probability of finding a certain particle in a certain place. In other words, the probability of a particle being in a predicted location makes it a wave, but its physical appearance and shape are not.
What is wave-particle duality?
While mathematics, albeit in an extremely complex way, makes accurate predictions based on differential equations, the meaning of these equations for quantum physics is much more difficult to understand and explain. An attempt to explain what wave-particle duality is remains at the center of the debate in quantum physics to this day.
The practical significance of wave-particle duality also lies in the fact that any physicist must learn to perceive reality in a very interesting way, when thinking about almost any object in the usual way is no longer enough for an adequate perception of reality.